Technical Field
This invention relates to an improved form of parboiled rice and a process for preparing it. In particular, the parboiled rice of the invention cooks rapidly, and yet is free of starchiness.
There are many recipes and occasions for which rice is so highly preferred that it seems indispensable. The art has long endeavored to improve upon natural raw rice in terms of its cooking and eating qualities. Up to the present time, however, it has not been possible to produce a rapidly cooking rice which is non-starchy and yet has a texture comparable to parboiled rice.
Parboiled rice is typically prepared by soaking rough rice paddy (unhulled rice, substantially as it comes from the field) in cold, warm or hot water for a substantial period of time, until the rice kernels have increased their moisture content, generally to at least above 20%; steaming the rice, generally at super-atmospheric pressure, to gelatinize the rice; and then drying the rice. The steaming partially opens the hulls and subsequent to steaming the kernels are dried and then milled.
Raw rice which is not parboiled, but is milled in the dry raw state, is generally quite rapidly cooked. Typically, cooking times of around 10 to 15 minutes will be achieved; however, the rice resulting from this process is extremely starchy tasting. It is believed that water enters the individual starch granules within the rice kernels and causes them to swell, then burst releasing free molecular starch and yielding a very starchy, pasty feel in the mouth. The starch in the raw milled rice, as stated in the name, is essentially ungelatinized (raw). When the rice is ground and tested by amylograph analysis on a Brabender Viscometer in standard fashion, the ground rice will show a breakdown value of within the range of from about 250 to 500 brabender units. The amylograph breakdown value is the difference in viscosity, as recorded on the amylograph curve, between the peak viscosity and viscosity after a hold time, which is believed indicative of the amount of starch granules which have ruptured causing the reduction in viscosity. The free molecular starch released as the starch granules rupture causes starchiness, thus the breakdown value is directly proportional to the starchiness of the hydrated rice. This test is carried out by: grinding 50 grams of milled rice and blending with 450 ml. of distilled water; placing the sample in the Brabender Viscometer which is set at a starting temperature of 30.degree. C.; and then heating and holding in the standard fashion (see Halick and Kelly, Cereal Chem. 36 (1), 1959 and Ferrel and Pence, Cereal Chem. 41 (1), 1964).
Parboiled rice, shows a great degree of improvement in its freedom from starchiness as evidenced by amylograph breakdown values of around 0 brabender units or even a slightly negative value (indicating an increase in viscosity after hold time). In the case of a negative amylograph breakdown value not only are starch granules remaining unbroken, but they continue to swell. This advantage in organoleptic improvement is, however, offset to a degree by the increased cooking time required to fully rehydrate the dry parboiled rice to achieve a cooked product. Typically, parboiled rice will require from 20 to 25 minutes to reach full hydration.
A quicker-cooking parboiled rice on the order of about 15 minutes can be achieved by reducing the severety of the parboiling procedure, however, the ultimately cooked parboiled rice becomes starchy. Typically, the quicker cooking parboiled rice prepared in this manner shows very high amylograph breakdown values, being at least 150 brabender units and typically being around 200 brabender units and higher.